Tens of thousands of people have died in El Salvador's civil war, but the deaths of four women there in December 1980 brought the outrage of the violence home to the United States more than the others did. The victims were Americans, they were Roman Catholic missionaries, and three were nuns.

They were, in short, the kind of people presumed to be immune to the death squads operating in a symbiotic relationship of tolerance and deniability by the U.S.-backed Salvadoran government. "They don't shoot blond, blue-eyed North American women," one of the victims, Jean Donovan, of Westport, Conn., and Cleveland, Ohio, once quipped to a friend.

The quotation opens "Roses in December--The Story of Jean Donovan," broadcast tonight at 9 on Channel 32 and again at 10 p.m. Tuesday on Channel 26. The program, first in a series of 10 documentaries entitled "Crisis to Crisis," probes the special terror the breakdown of that presumed immunity caused for an American family. Interspersed throughout the film as a kind of leitmotif is excruciating documentary footage of the discovery of the four churchwomen's bodies in a common grave in a field outside of San Salvador.

Six members of El Salvador's National Guard were placed under arrest, but have not yet been tried, after investigators obtained confessions from several of the soldiers that they participated in murdering and raping Donovan, Ursuline sister Dorothy Kazel and Maryknoll sisters Ita Ford and Maura Clark the night of Dec. 2, 1980.

The murders, the investigation and an aftermath of controversial statements on the case by U.S. officials, including then-secretary of state Alexander M. Haig Jr., have become a centerpiece in the debate over U.S. aid to the Salvadoran government in fighting leftist guerrillas.

The film's poignancy is powerful, but in measured proportion to the real-life drama of the other kind of American involvement in El Salvador, the involvement of young religious idealists like Donovan.

The hour-long film uses interviews with friends and family, Donovan's diary and letters home, snapshots and home-movie footage to build a portrait of Americana. Jean Donovan, born to suburban affluence, a gregarious young woman embarked on an upscale business career, joins a lay missionary organization in order to spend several years helping the poor in El Salvador, where she is brutalized.

The documentary makes its political points softly in the U.S. debate. Criticisms of the Reagan administration's handling of the case are expressed in the restrained outrage of Donovan's brother, Michael Donovan, a Danbury, Conn., accountant, and William Ford, a Wall Street lawyer who is Ita Ford's brother.

"We were supporting a government, that government killed my sister, and my government didn't care . . . . I can't tell you how difficult that is for me to accept as an ordinary American citizen," Ford says.

In early 1981, Haig, as secretary of state, testified before a congressional committee that the deaths might have occurred when the women ran a military roadblock--a theory Donovan and Ford say contradicted evidence already developed by U.S. investigators at that time.

The statement, and an earlier assertion by Representative to the United Nations-designate Jeane Kirkpatrick that the churchwomen were "not just nuns, they were political activists," are the only statements by Reagan administration officials included in the film and inevitably tend to carve an image of official callousness in the case. The State Department declined to have any officials interviewed on camera, coproducer David Meyer said.

Last month, in a point not covered in the film, Donovan, Ford and other family members sued the U.S. government to obtain information about the investigation of the murders that they claim has been withheld by the State Department